The present invention relates generally to electrophotographic image-forming devices, and more particularly to a method of controlling a post-processor that handles continuous paper printed by an electrophotographic image-forming device.
The present invention is suitable, for example, for an output device for use with a computer system that needs to print large amounts of data.
Hereupon, the xe2x80x9celectrophotographic image-forming devicexe2x80x9d by which we mean is an image-forming device employing the Carlson process described in U.S. Pat. No. 2,297,691, and denotes a nonimpact printer that provides recording by depositing a developer as a recording material on a recordable medium (continuous paper in the present invention). The xe2x80x9ccontinuous paperxe2x80x9d includes fanfold paper and paper in rolls, and denotes a recordable medium that permits a user""s discretionary setting of a recording length. The width of the continuous paper is determined by selecting a type of paper to be used, as necessary, from several types of ready-made paper that have a standardized or predetermined width.
The xe2x80x9cpost-processorxe2x80x9d is a device that carries out one or more of various operations such as cutting, sorting, stapling, etc. after recording on the continuous paper. Characteristically, the post-processor is connected with an image-forming device, and carries out an operation under the control of the image-forming device as a host processor.
In recent years, the electrophotographic image-forming device (continuous paper printer) that uses continuous paper as a recordable medium for printing large amounts of data is typically connected with the post-processor that automatically carries out one or more of various operations such as folding, cutting, sorting, and stapling for the continuous paper. The electrophotographic continuous paper printer, which generally uses a photoconductive insulator (e.g., photosensitive drum, and photosensitive belt), follows the procedural steps of charging, exposure to light, development, and transfer, and the process further includes the fixing step for the continuous paper after the transfer step.
The charging step uniformly electrifies the photosensitive drum (e.g., at xe2x88x92700V). The exposure step irradiates a laser beam or the like on the photosensitive drum, and changes the electrical potential at the irradiated area down, for example, to xe2x88x9250V or so, forming an electrostatic latent image. The development step electrically deposits a developer onto the photosensitive drum using, for example, the reversal process, and visualizes the electrostatic latent image. The transfer step forms a toner image corresponding to the electrostatic latent image on a recordable medium using a transfer unit. The fixing step fuses and fixes the toner image on the medium by the application of heat or pressure, or light irradiation by a fixing unit, thereby obtaining a printed matter.
Conventionally, one printing operation in the continuous paper printer that forms an image on the continuous paper is defined as a process going on after a toner image is transferred from the photosensitive drum to the continuous paper until the fixing unit fixes the toner image. When a print command for one job has been finished, and a subsequent print command for the next job has not been received, the continuous paper on which the last line is printed is at a standstill on a continuous paper feed path in the continuous paper printer. To be more specific, the paper feed stops immediately after the last line has passed through the fixing unit. However, when the command for the next job is issued in this situation, and the printing starts, a blank area in which no image is formed is produced between the last line of the image printed by the immediately preceding job, and the first line of the image to be printed by the next job on the continuous paper. This would waste the continuous paper with a length corresponding to a distance from the fixing unit to a transfer position, and thus impair the use efficiency of the continuous paper. Therefore, a so-called reverse feed has conventionally been carried out that moves back the continuous paper by a specific length when a print command for one job is completed, and no print command for the next job comes. This would improve the use efficiency of the continuous paper.
To give another example, a continuous paper printer that includes first and second image-forming parts, and sequentially records images on both sides of the continuous paper forms the images in each image-forming part spaced out due to mechanical requirements. To be specific, the two-sided printer forms images by following the steps of a transfer on a first side of paper by a first image-forming part, a transfer on a second side of paper by a second image-forming part, a fixing on the first side of paper by the first image-forming part, and a fixing on the second side of paper by the second image-forming part in this sequence. In order to improve the use efficiency of continuous paper in the printer configured as above, the reverse feed amount of the continuous paper (distance at which the continuous paper is conveyed in a backward direction) is configured to be larger than that in a single-side printer.
The post-processor is electrically connected with the continuous paper printer, and carries out operations such as cutting of the continuous paper conveyed. Following is an exemplified post-processor embodied as a burster unit that separates the continuous paper along perforations into individual sheets. The burster unit upon startup of the printing operation simultaneously starts separation of the continuous paper conveyed; thus, the continuous paper has already been separated when the reverse feed is to be carried out in the continuous paper printer, and cannot be conveyed in a reverse direction. Therefore, if the post-processor having no reverse feed capability is connected with the continuous paper printer having a reverse feed capability, the feed of the continuous paper is controlled so that a reverse feed amount of the continuous paper may sag during printing. In addition, the post-processor is manufactured by a maker other than that of the continuous paper printer in many occasions, and thus may be selected among post-processors capable of accepting a specific post-processing command from the continuous paper printer.
A further detailed description will be given of the method of controlling the post-processor with reference to FIG. 9. FIG. 9 is a flowchart showing a conventional method of controlling printing operations for explaining the method of controlling the post-processor, where the reverse feed amount (distance from the transfer part to the fixing part) is 50 inches. First, for example, when a print command for one job is issued from a host device such as a computer (step 2), the continuous paper printer receives the command to initiate printing (step 4). Subsequently, the image-forming device, which has experimentally worked out the time required to feed continuous paper over a predetermined distance of 50 inches in advance, sets a timer for that time (step 6). The image-forming device then initiates the operation, and does printing as intended on the continuous paper (step 8). During the printing operation, if the timer exceeds the set time and indicates zero (step 10), the image-forming device, construing it to mean that a 50-inch sag has been formed in the continuous paper, transmits a signal to initiate an operation to the post-processor. Until the timer indicates zero (step 10), the printing operation continues all the way, and the signal to initiate the operation is not transmitted to the post-processor. The post-processor eventually receives the command to initiate the operation, and initiate the operation (e.g., of cutting the continuous paper) (step 12). If the intended printing operation is completed, the paper feed stops immediately after the last line of the image on the continuous paper has passed through the fixing part. At that moment, the image-forming device and post-processor simultaneously stops the operations. Thereafter, a feeder unit in the image-forming device initiates an operation, and carries out a reverse feed for a distance of 50 inches to get ready for the print command for the next job. The intended printing based upon the command from the host device is then completed (step 14). As has been described above, the printing operation for the continuous paper repeats a series of these procedural steps.
However, since a sag the amount of which corresponds to the reverse feed amount is continuously provided in the continuous paper while the printing operation is carried out according to the conventional method, if the image-forming device of which the reverse feed amount is large is used, or if there is a difference in processing speed between the continuous paper printer and the post-processor, and the former is faster than the latter, then part of the continuous paper comes in contact with the floor between the image-forming device and the post-processor. Consequently, the printed surface of the continuous paper and the floor rubs together, and disadvantageously disturbs an image or smears the printed surface. In order to provide a means for avoiding this problem, a saucer made of sheet metal or the like is placed on the floor so that the continuous paper ejected from the image-forming device may not get in direct contact with the floor. Nonetheless, the printed continuous paper is constantly in contact with and rubbed against the saucer during the printing operation, and thus there exists high possibilities that the image quality would lower, the continuous paper would smear, and the other problems would occur. In addition, the large amount of the sag in the continuous paper would disadvantageously increase the effect of the wind from outside, or the like, and prevent a stable movement of the continuous paper, thereby producing a jam in the post-processor.
There is a method of removing an excess sag in the continuous paper, in which the continuous paper is not brought into contact with the floor due to a mechanical buffer mechanism provided for a sagged portion in the continuous paper. However, the method would disadvantageously result in increased costs for providing the buffer mechanism. Another method of avoiding the sag problem is conceivable, in which the post-processor is also provided with the reverse feed mechanism, but the continuous paper that has already undergone the post-process such as cutting cannot be conveyed in the reverse direction, and therefore the current practice adopts the aforementioned controlling method at the same time to avoid the problem.
Accordingly, it is an exemplified general object of the present invention to provide a novel and useful post-processor connectible with an image-forming device in which the above disadvantages are eliminated.
Another exemplified and more specific object of the present invention is to provide a method of controlling a post processor connectible with an image forming device that utilizes a conventional image-forming device and post-processor, and dispenses with a sag to be formed in continuous paper all the time during printing operation.
In order to achieve the above objects, a method of controlling a post-processor as one exemplified embodiment of the present invention is carried out by an image-forming device that includes a transfer part and a fixing part, and conveys continuous paper. The image-forming device is connected with the post-processor that carries out processing on continuous paper on which an image has been formed. This method comprises the steps of initiating an electrophotographic image-forming operation in the transfer part and the fixing part so that the image-forming device forms an image onto and conveys the continuous paper, initiating an operation of the post-processor so that the post-processor post-processes and conveys the continuous paper, stopping the operation of the post-processor on or before completion of a transfer by the transfer part onto the continuous paper, conveying to the fixing part the continuous paper onto which the transfer part has finished transferring, and conveying to the transfer part the continuous paper onto which the fixing part finishes a fixation. According to this control method, the continuous paper is conveyed from the transfer part to the fixing part after the operation of the post-processor has stopped, to provide a sag in the continuous paper between the image-forming device and the post-processor, and thus is prevented from being cut off even if the continuous paper is conveyed in a reverse direction from the fixing part to the transfer part to get ready for a print command for the next job.
An image-forming device as one exemplified embodiment of the present invention in order to achieve the above objects is an electrophotographic image-forming device comprises a mechanical controller which controls a printing mechanism that forms an image, and a conveyor mechanism that conveys a continuous paper, and a main controller that controls the mechanical controller. The main controller controls the mechanical controller so as to generate a signal for stopping a conveyance by a post-processor connected with the image-forming device a specified time before the conveyor mechanism stops. This image-forming device may generate the signal for stopping the conveyance of the post-processor prior to stopping a conveyance mechanism of the image-forming device, and thus be connected with and control the post-processor without any changes such as an addition of parts or modification to a conventional post-processor.
Other objects and further features of the present invention will become readily apparent from the following description of the embodiments with reference to accompanying drawings.